The present invention relates to electrostatic precipitators and, more particularly, to an apparatus for tensioning the discharge electrode wires of a rigid-frame type electrostatic precipitator. In the operation of an electrostatic precipitator, a gas laden with entrained particulate material is passed through an electrostatic field established about a discharge electrode disposed between two grounded collecting electrodes. The suspended particles become electrically charged as they pass through the electrostatic field and move to, under the influence of the electrostatic field, and deposit upon the grounded collecting electrodes flanking the discharge electrode.
Typically, each collecting electrode is formed of one or more elongated plates disposed in a row side by side and suspended from the top of the precipitator housing in a vertical plane. A plurality of such collecting electrodes are disposed transversely across the precipitator casing in spaced vertical planes parallel to the direction of the gas flow through the precipitator.
In what is commonly referred to as a rigid-frame electrostatic precipitator, a box-like framework comprised of a plurality of discharge electrode frames is suspended from insulators at the top of the precipitator housing to provide a row of vertically disposed discharge electrodes between adjacent collecting electrodes across the width of the precipitator. A voltage is applied to the discharge electrodes to generate the electrostatic field.
Each discharge electrode frame is comprised of a plurality of individual discharge electrode wires tautly strung across a support frame. As the electrode wires are installed at ambient temperature but typically operated at temperatures in the range of 150C to 250C, the discharge electrode wires may elongate due to thermal expansion and therefore become loose. Discharge electrode wires may also become loose due to handling during erection and shipment of the rigid discharge electrode frames.
Although a loose wire will not impede the dust collection process per se, a loose discharge electrode wire will not respond well in the rapping process. It is typical to periodically rap the discharge electrode frame to vibrate off any dust collecting on the discharge electrode wires as the collection of dust thereon can result in severe arcing between the discharge electrode wire and its neighboring collecting electrodes or in the shorting of electrostatic field by bridging of dust deposits between the discharge electrode wire and its neighboring collecting electrodes. A loose discharge electrode wire, however, will not vibrate as well as, and therefore not clean as easily as, a properly taut discharge electrode wire.
The typical prior art solution to the problem of loose discharge electrode wires is to shut the electrostatic precipitator down and re-tension the wires manually, one at a time, by re-welding or twisting the discharge electrode wires to take up the looseness. Of course, this is a time-consuming, labor intensive task. Additionally, in severe cases of loss of tension in the discharge electrode wires, it may be necessary to replace the entire discharge electrode frame in which the loose wires are located.